Macular degeneration is the leading cause of blindness in people over the age of 55 in the United States and affects more than 10 million Americans. It is caused by deterioration of the central portion of the retina. The retina contains a photosensitive array of cells lining the back of the eye. As light falls on these cells, it is transformed into electrical signals which are relayed to the vision centers of the brain.
The central portion of the retina is known as the macula. The macula is a small region of the retina and is responsible for focusing central vision in the eye. Degenerative changes in the macula such as caused by macular degeneration, accounts for the vast majority of sight threatening changes in the population over age 50.
Macular degeneration presents as two basic types: "dry" and "wet". Most cases of macular degeneration, approximately 85-90% of all cases, are the "dry" (atrophic) type. The deterioration of the retina in the "dry" type of macular degeneration occurs due to the formation of small yellow deposits known as drusen which form in the macula, resulting in a thinning and drying out of the macula. The amount of vision loss is directly related to the amount and location of the retinal thinning caused by the drusen. The progressive vision loss associated with the "dry" type of macular degeneration tends to progress much more slowly than the "wet" type, and there is no known treatment or cure for the "dry" type of macular degeneration.
The "wet" type of macular degeneration is due to the growth of abnormal blood vessels under the retina and macula, known as subretinal neovascularization. Leaking fluid or blood from these blood vessels cause the macula to bulge or lift up with resulting distortion or loss of central vision. Unlike the "dry" type, the "wet" type of macular degeneration may have rapid and severe vision loss. While the "wet" type of macular degeneration may be treated with laser therapy, these therapies are limited in effectiveness, and serve mainly to slow the rate of vision loss.
In the "dry" type of macular degeneration, as parts of the macula begin to die, blank spots appear in the central portion of vision. Additionally, the central vision may appear blurry and straight lines may look wavy. Peripheral or side vision is rarely affected. In the "wet" type of macular degeneration the macula is no longer smooth, as a result, straight lines may also look wavy, similar in appearance to the "dry" type. Due to blood or fluid under the macula, in the "wet" type, the patient may see a dark spot or spots in the center of their vision. As in the "dry" type of macular degeneration, peripheral or side vision is rarely affected.
Attempts have been made to increase the quality of life of patients suffering from macular degeneration by refocusing light rays onto healthy peripheral portions of the eye, for example, by utilizing prismatic lenses. U.S. Pat. Nos. 5,155,508 and 5,323,190 to Onufryk; U.S. Pat. Nos. 4,772,113 and 4,958,924 to Parker, and U.S. Pat. No. 4,779,972 to Gottlieb all disclose prismatic lenses to redirect light. These prismatic lenses are technically difficult and expensive to manufacture, and once made, they focus light rays to only a pre-selected peripheral portion of the eye. As degenerative changes continue, redirecting light rays to the remaining healthy portions of the eye requires manufacture of new prismatic lenses at considerable additional expense.
U.S. Pat. No. 4,673,263 to Onufryk relates to utilizing paired angle mirrors as part of diagnostic machinery to determine which peripheral areas of the eye remain healthy. An optical image deflecting assembly is provided having a fixed light reflecting optical element, such as a mirror, and a pivotal reflecting optimal element, such as a mirror. Light received from one of the mirrors is reflected onto a peripheral area of an eye for scanning an arcuate portion of the area upon pivotal movement of the pivotal mirror. The pivotal optical element is pivoted at incremental positions for scanning an annular peripheral area of each eye and locating the most visually sensitive areas.
Other diseases resulting in visual loss have also been treated utilizing mirrors, for example, homonymous hemianopsa A patient suffering homonymous hemianopsa loses sight on the same side of the normal visual field of both eyes, producing only half a field of vision from each eye. U.S. Pat. No. 4,155,633 to Benavie discloses two spaced reflectors whose pivot axis is disposed in a generally vertical plane. The reflectors are positioned in front of only one of the two affected eyes in a manner such that one or both of the reflectors block the direct field of view seen by only one of the eyes, i.e., the field that would be seen by one of the eyes in the absence of the corrective device, and substitute a virtual image of an additional horizontal angle sight which is outside the uncorrected limited visual field of view.
Although the existing art discloses the use of paired angled reflecting mirrors to reflect an image onto a peripheral area of an eye, these mirrors are used for diagnostic purposes and not in conjunction with eyeglass wear. One mirror is fixed and the other is rotatable, thus limiting the ability to redirect light rays.
What is needed is a simple, affordable device to redirect light rays to the healthy peripheral portion of an eye in patients suffering from macular degeneration, adjustable as vision continues to deteriorate without the need for costly replacement of the entire unit.